WO2021075971A1

WO2021075971A1 - Vibrating system and method for inserting a foundation element into the ground using flexible elements

Info

Publication number: WO2021075971A1
Application number: PCT/NL2020/050643
Authority: WO
Inventors: Laurens De Neef
Original assignee: Cape Holland Holding BV
Current assignee: Cape Holland Holding BV
Priority date: 2019-10-18
Filing date: 2020-10-19
Publication date: 2021-04-22
Anticipated expiration: 2022-04-18
Also published as: EP4045721A1

Abstract

The invention relates to a vibrating system (2) for inserting a foundation element (12) into the ground and an associated method. The vibrating system according to the invention comprises: • - a vibrating device (20); • - a drive operatively connected to the vibrating device and configured for driving the vibrating device; • - coupling (24) configured for connecting the vibrating device (20) with the foundation element (12), wherein the coupling comprises a flexible element (24).

Description

Vibrating system and method for inserting a foundation element into the ground using flexible elements

The invention relates to a vibrating system for inserting a foundation element, such as a foundation pile for a wind turbine, into the ground. Such foundation elements can be inserted into the ground on land or at sea.

Vibrating systems as such are known in practice. These systems make use of a vibrating device and more particularly of a vibrator block provided with a number of eccentrics. Such a vibrator block exerts vibrations on the foundation element, whereby this element is vibrated into the ground. These vibrator blocks are usually arranged as rigid as possible on the upper side of the foundation element during insertion thereof.

The vibrating systems known in practice are usually driven hydraulically, wherein use is made of a so-called power pack comprising a diesel engine and a hydraulic pump. This hydraulic pump drives the hydraulic motor of the vibrating device.

The vibrator devices create vibrations with a frequency that may bring the foundation element into resonance. Resonating frequency changes with the penetration depth of the pile due to the increasing influence of the soil on the foundation element surface. This makes it difficult to prevent undesired resonance of the foundation element.

Another disadvantage of this method is the appearance of high stress values in the foundation element due to the large stain caused by the resonance. This results in a larger fatigue damage, which could mean that the strength of the foundation element has to be increased which would make it more costly and harder to handle. This is especially problematic in off-shore applications. Pile resonance can also result in higher pile deflections, which can result in higher under water noise emissions. This may harm sea live.

A further problem with conventional vibrating systems is that they cannot handle variable conditions flexibly. Such variable conditions can be a local variation in ground condition and/or a ground layer with a greater resistance to insertion of the foundation element. The greater resistance entails the danger of overloading of the hydraulic system and reaching the pressure limits, so that a safety valve will open and some of the hydraulic oil is discharged, preferably back to the hydraulic oil reservoir. This increases the insertion time of the foundation element and in addition increases the amount of energy required for this purpose.

An object of the present invention is to obviate or reduce the above stated problems and to provide an effective vibrating system for inserting a foundation element into the ground.

This object is achieved with the vibrating system for inserting a foundation element into the ground according to the present invention, wherein the vibrating system comprises: a vibrating device; a drive operatively connected to the vibrating device and configured for driving the vibrating device; coupling configured for connecting the vibrating device with the foundation element, wherein the coupling comprises a flexible element.

According to the invention a flexible element is provided between the vibrating device and the foundation element, in particular the upper side thereof. This provides a flexible coupling or connection between the vibrating device and the foundation element, such as a foundation pile, a foundation tube and a sheet pile profile. The flexible connection is made in such a way that the vibration of the vibrating device is amplified or resonates due to the flexible connection and hence the vibratory effect on the foundation element is increased above that which is possible by making a conventional fixed/rigid connection. An advantage is that the vibrating system of the invention may insert a foundation element with the use of less energy consumption as compared to conventional systems.

A further advantage of the system according to the invention is that the spring stiffness of the flexible connection is not (significantly) affected by the soil and potential high stresses will be concentrated in the flexible connection. Hereby, the disadvantages of resonating the foundation element are obviated. This reduces the insertion time required for inserting the foundation element into the ground and/or reduces the energy required for the insertion in a wide operating range of occurring conditions, such as insertion resistance. An effective vibrating system is hereby provided.

In a preferred embodiment of the invention the flexible element has spring and damping characteristics.

Providing the flexible elements introduces spring and damping characteristics between the vibrating device and the foundation element. This enables the increase of the vibratory effect on the foundation element. This reduces the amount of energy consumption that is required to insert a foundation element into the ground. Also, it may reduce the noise emission of the insertion process. Furthermore, it may shorten the time period that is required for inserting the foundation element into the ground. The number of elements can be determined in view of the vibrating device and the foundation element, for example.

Preferably, the flexible element comprises rubber elements. These rubber elements are effective and efficient to provide the desired spring and damping characteristics between the vibrating device and the foundation element. Alternatively, the flexible element comprises steel elements (such as steel springs) and/or composite elements. In a further alternative embodiment of the invention the flexible element comprises a gas element. Such gas element may behave like a gas cylinder and is positioned between the vibrating device and the foundation element. In an even further alternative embodiment of the invention the flexible element comprises a (electro)- magnetic spring system. Optionally, a combination of two or more of these flexible elements is applied in an embodiment of the invention.

In a presently preferred embodiment the vibrating device comprises a number of eccentrics.

The vibration source is the vibrating device with in this embodiment the eccentrics. Vertical oscillation of a vibration device is often generated by means of the pairwise installed eccentric weights that rotate in a vertical plane to create vibration.

Alternatively a vertical linear resonator or other type vibrating elements can be used, which makes it possible to integrate the flexible element directly to the vibrating weight. In such alternative embodiment the vibrating device comprises a vibrator block that acts as the vibrating element. The vibrator block may comprise one or more linear vibrating weights. The weights can be used in combination with the flexible elements that may comprise rubber elements, gas elements etc.

In a presently preferred embodiment of the invention the drive of the vibrating device, formed by the motor, comprises a hydraulic motor, a (hydraulic) pump, and the drive unit that produces a quantity of hydraulic fluid which determines the frequency of the vibrating device. The effective frequency of the vibrating device is determined in practice by the relation between the quantity of hydraulic fluid and the so-called stroke volume of the hydraulic motor, together with the transmission ratio inside the vibrating device. The frequency of the vibrating device together with the eccentric moment of the vibrating device determines the impact force, i.e. the power produced by the vibrating device. It will be understood that other drives can be used as an alternative or in addition, including electric and pneumatic drives.

In an advantageous preferred embodiment according to the present invention the vibrating system comprises a control system configured to modify the drive force of the vibrating system. Providing a control system enables the adjusting device to be controlled in effective manner. The control system is preferably provided with a pressure sensor whereby it is possible to determine the current operating pressure and, also on the basis thereof, perform the adjustment of the stroke volume of the hydraulic motor in particular. An effective and efficient modification of the settings of the vibrating system according to the invention can be realized in this way.

The invention further relates to a method for varying the drive force of a vibrating system for inserting a foundation element into the ground, wherein the method comprises the steps of: providing a vibrating system according to an embodiment of the invention; and enhancing the vibrating effect of the vibrator element with the flexible elements between the vibrating device and the foundation element.

The method provides the same advantages and effects as described for the vibrating system. The application of the flexible element enhances the vibrational movements, thereby providing an optimal power take-up by the foundation element, which preferably remains substantially constant under variable conditions. A foundation element can hereby be placed in the ground in effective manner with a short insertion time and/or minimal energy consumption.

Further advantages, features and details of the invention are elucidated on the basis of a preferred embodiment thereof, wherein reference is made to the accompanying figures in which: Figure 1 shows a view of a vibrating system according to the invention;

Figure 2 A-D shows a view of an alternative vibrating system according to the invention, Figure 2 C being a cross-sectional view along A- A in Figure 2 B, and Figure 2 D being a cross-sectional view along B-B in Figure 2 B; and Figure 3 A-C show schematic overviews of alternative vibrating devices for the vibrating system according to the invention.

Vibrating system 2 (Figure 1) comprises an outer suppressor 4 that is coupled to inner suppressor 8 via spring elements 6 that prevent vibrations to reach the boom of the lifting device, for example. Inner suppressor 8 is mounted on carter 10 of frame 14. Clamps 16 of clamping mechanism 18 clamp foundation pile 12. In the illustrated embodiment connections between inner suppressor 8, carter 10, frame 14, clamps 16 of clamping mechanism 18 and foundation pile 12 are rigid. Only between vibrator device 20 with eccentrics 22 and connected to carter 10 and frame 14 there is provided a number of flexible elements 24. In the illustrated embodiment elements 24 are made of a rubber material.

In an alternative embodiment of the invention (Figure 2A-D) vibrating system 2 comprises vibrating device 20 with eccentrics 22 that is mounted on plate 26. Between plate 26 and connector 28 there are provided a number of flexible elements 24. Connector 24 can be connected to a foundation element via flange 30. It will be understood that also a clamp coupling could be envisaged, for example like claiming mechanism 18. Vibrating system 2 is further provided with controller 32.

Vibrating device 20 (Figure 3 A) comprises a number of eccentrics 34. Between vibrating device 20 and pile 12 there are provided a number of flexible elements 24 providing spring characteristics 24a and damping characteristics 24b to vibrating system 2.

In an alternative embodiment vibrating device 20 (Figure 3B) comprises a number of linear vibrating weights 36. Between vibrating device 20 and pile 12 there are provided a number of flexible elements 24 providing spring characteristics 24a and damping characteristics 24b to vibrating system 2.

In a further alternative embodiment vibrating device 20 (Figure 3C) comprises a number of linear weights 36 directly connected to a number of flexible elements 24. This provides an integrated system. In the illustrated embodiments eccentrics 34 and/or weights 36 can be drive hydraulically, and also electrically or pneumatically, or by combinations thereof. Optionally, weights move in a cylinder type chamber 38 using a gas force.

In use, vibrating system 2 is connected to foundation element 12. When started, vibrating device 20 starts to vibrate. Vibrations are lead to pile 12 that is therewith inserted into the ground. The flexible connection with flexible elements 24 between vibrating device 20 and pile 12 is made in such a way that the vibration of the vibrating device is amplified or resonates due to the flexible connection and hence the vibratory effect on the foundation element is increased above that which is possible by making a conventional fixed/rigid connection. Tests have shown that the vibrating system of the invention may insert a foundation element with the use of less energy consumption as compared to conventional systems.

The invention is by no means limited to the above described preferred embodiments thereof. The rights sought are defined by the following claims, within the scope of which many modifications can be envisaged.

Claims

1. Vibrating system for inserting a foundation element into the ground, comprising: a vibrating device; a drive operatively connected to the vibrating device and configured for driving the vibrating device; coupling configured for connecting the vibrating device with the foundation element, wherein the coupling comprises a flexible element.

2. Vibrating system as claimed in claim 1, wherein the flexible element has spring and damping characteristics.

3. Vibrating system as claimed in claim 1 or 2, wherein the flexible element comprises rubber elements.

4. Vibrating system as claimed in claim 1, 2 or 3, wherein the flexible element comprises a gas element.

5. Vibrating system as claimed in one or more of the foregoing claims, wherein the flexible element comprises a steel, magnetic, and/or electro spring.

6. Vibrating system as claimed in one or more of the foregoing claims, wherein the vibrating device comprises a number of eccentrics.

7. Vibrating system as claimed in one or more of the foregoing claims, wherein the vibrating device comprises a vibrator block.

8. Vibrating system as claimed in claim 7, wherein the flexible elements are integrated with the vibrator block.

9. Method for inserting a foundation element into the ground, comprising the steps of: providing a vibrating system as claimed in one or more of the foregoing claims; and enhancing the vibrating effect of the vibrator element with the flexible elements between the vibrating device and the foundation element.

10. Apparatus and/or method for inserting a foundation element into the ground according to the description and/or accompanying drawings.